/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.thinkinbunny.codec.net;

import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;

import org.thinkinbunny.codec.Charsets;
import org.thinkinbunny.codec.DecoderException;
import org.thinkinbunny.codec.EncoderException;
import org.thinkinbunny.codec.StringDecoder;
import org.thinkinbunny.codec.StringEncoder;
import org.thinkinbunny.codec.binary.Base64;

/**
 * Identical to the Base64 encoding defined by <a
 * href="http://www.ietf.org/rfc/rfc1521.txt">RFC 1521</a> and allows a
 * character set to be specified.
 * <p>
 * <a href="http://www.ietf.org/rfc/rfc1522.txt">RFC 1522</a> describes
 * techniques to allow the encoding of non-ASCII text in various portions of a
 * RFC 822 [2] message header, in a manner which is unlikely to confuse existing
 * message handling software.
 * <p>
 * This class is immutable and thread-safe.
 * 
 * @see <a href="http://www.ietf.org/rfc/rfc1522.txt">MIME (Multipurpose
 *      Internet Mail Extensions) Part Two: Message Header Extensions for
 *      Non-ASCII Text</a>
 * 
 * @since 1.3
 * @version $Id: BCodec.java 1380305 2012-09-03 18:37:21Z tn $
 */
public class BCodec extends RFC1522Codec implements StringEncoder,
		StringDecoder {
	/**
	 * The default charset used for string decoding and encoding.
	 */
	private final Charset charset;

	/**
	 * Default constructor.
	 */
	public BCodec() {
		this(Charsets.UTF_8);
	}

	/**
	 * Constructor which allows for the selection of a default charset
	 * 
	 * @param charset
	 *            the default string charset to use.
	 * 
	 * @see <a
	 *      href="http://download.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard
	 *      charsets</a>
	 * @since 1.7
	 */
	public BCodec(final Charset charset) {
		this.charset = charset;
	}

	/**
	 * Constructor which allows for the selection of a default charset
	 * 
	 * @param charsetName
	 *            the default charset to use.
	 * @throws java.nio.charset.UnsupportedCharsetException
	 *             If the named charset is unavailable
	 * @since 1.7 throws UnsupportedCharsetException if the named charset is
	 *        unavailable
	 * @see <a
	 *      href="http://download.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard
	 *      charsets</a>
	 */
	public BCodec(final String charsetName) {
		this(Charset.forName(charsetName));
	}

	@Override
	protected String getEncoding() {
		return "B";
	}

	@Override
	protected byte[] doEncoding(byte[] bytes) {
		if (bytes == null) {
			return null;
		}
		return Base64.encodeBase64(bytes);
	}

	@Override
	protected byte[] doDecoding(byte[] bytes) {
		if (bytes == null) {
			return null;
		}
		return Base64.decodeBase64(bytes);
	}

	/**
	 * Encodes a string into its Base64 form using the specified charset. Unsafe
	 * characters are escaped.
	 * 
	 * @param value
	 *            string to convert to Base64 form
	 * @param charset
	 *            the charset for <code>value</code>
	 * @return Base64 string
	 * @throws EncoderException
	 *             thrown if a failure condition is encountered during the
	 *             encoding process.
	 * @since 1.7
	 */
	public String encode(final String value, final Charset charset)
			throws EncoderException {
		if (value == null) {
			return null;
		}
		return encodeText(value, charset);
	}

	/**
	 * Encodes a string into its Base64 form using the specified charset. Unsafe
	 * characters are escaped.
	 * 
	 * @param value
	 *            string to convert to Base64 form
	 * @param charset
	 *            the charset for <code>value</code>
	 * @return Base64 string
	 * @throws EncoderException
	 *             thrown if a failure condition is encountered during the
	 *             encoding process.
	 */
	public String encode(final String value, final String charset)
			throws EncoderException {
		if (value == null) {
			return null;
		}
		try {
			return this.encodeText(value, charset);
		} catch (UnsupportedEncodingException e) {
			throw new EncoderException(e.getMessage(), e);
		}
	}

	/**
	 * Encodes a string into its Base64 form using the default charset. Unsafe
	 * characters are escaped.
	 * 
	 * @param value
	 *            string to convert to Base64 form
	 * @return Base64 string
	 * @throws EncoderException
	 *             thrown if a failure condition is encountered during the
	 *             encoding process.
	 */
	@Override
	public String encode(String value) throws EncoderException {
		if (value == null) {
			return null;
		}
		return encode(value, this.getCharset());
	}

	/**
	 * Decodes a Base64 string into its original form. Escaped characters are
	 * converted back to their original representation.
	 * 
	 * @param value
	 *            Base64 string to convert into its original form
	 * @return original string
	 * @throws DecoderException
	 *             A decoder exception is thrown if a failure condition is
	 *             encountered during the decode process.
	 */
	@Override
	public String decode(String value) throws DecoderException {
		if (value == null) {
			return null;
		}
		try {
			return this.decodeText(value);
		} catch (UnsupportedEncodingException e) {
			throw new DecoderException(e.getMessage(), e);
		}
	}

	/**
	 * Encodes an object into its Base64 form using the default charset. Unsafe
	 * characters are escaped.
	 * 
	 * @param value
	 *            object to convert to Base64 form
	 * @return Base64 object
	 * @throws EncoderException
	 *             thrown if a failure condition is encountered during the
	 *             encoding process.
	 */
	@Override
	public Object encode(Object value) throws EncoderException {
		if (value == null) {
			return null;
		} else if (value instanceof String) {
			return encode((String) value);
		} else {
			throw new EncoderException("Objects of type "
					+ value.getClass().getName()
					+ " cannot be encoded using BCodec");
		}
	}

	/**
	 * Decodes a Base64 object into its original form. Escaped characters are
	 * converted back to their original representation.
	 * 
	 * @param value
	 *            Base64 object to convert into its original form
	 * @return original object
	 * @throws DecoderException
	 *             Thrown if the argument is not a <code>String</code>. Thrown
	 *             if a failure condition is encountered during the decode
	 *             process.
	 */
	@Override
	public Object decode(Object value) throws DecoderException {
		if (value == null) {
			return null;
		} else if (value instanceof String) {
			return decode((String) value);
		} else {
			throw new DecoderException("Objects of type "
					+ value.getClass().getName()
					+ " cannot be decoded using BCodec");
		}
	}

	/**
	 * Gets the default charset name used for string decoding and encoding.
	 * 
	 * @return the default charset name
	 * @since 1.7
	 */
	public Charset getCharset() {
		return this.charset;
	}

	/**
	 * Gets the default charset name used for string decoding and encoding.
	 * 
	 * @return the default charset name
	 */
	public String getDefaultCharset() {
		return this.charset.name();
	}
}
